Umbilical venous catheterization is a common procedure in the management of sick neonates. These catheters are commonly used for the administration of fluids, nutrition and medications, blood gas monitoring, and exchange transfusions (M. Butler O'Hara, C. J Buzzard, L. Reubens, M. P McDermot, W. DiGrazio and C. T. D'Angio. A is randomized trial comparing long-term and short-term use of umbilical venous catheters in premature infants with birth weights of less than 1251 grams, Pediatrics 2006; vol 118; no 1, p 25-35).
The umbilical cord comprises two umbilical arteries and one umbilical vein embedded in mucous connective tissue, so called Whartons jelly, in addition to endodermal remnants of the allantois, extending the length of the cord in humans. The cord is enveloped in a simple epithelium of amniotic derivation. Both the arteries and vein differ from the corresponding vessels in the body in that the arteries are carrying oxygen poor blood while the vein is carrying oxygen rich blood. Thus there are differences in the anatomy. Accordingly the arteries exhibits a comparatively thick muscularis, with intermingling circular, longitudinal and obliquely smooth muscle fibers. An internal elastic lamina is present, distinguishing the vein from the accompanying arteries. The mucous connective tissue is a form of loose connective tissue. The vessels have a helical course which impedes compressing of the vessels and make the cord stronger.
Immediately following birth, that is at 1, 5 and 10 minutes, the neonates are subjected to establishment of an Apgar score to judge the condition of the neonate. The score comprises an evaluation of the condition of the child within five different areas, such as heart rate, breathing effort, muscle tone, reflexes and skin color. Each condition is scored from 0-2 which is added to give a total score of 0-10. The neonate is retested after 5 minutes and if necessary subjected to further tests at 5 minutes intervals. The first test might give a low score which is normalized after 5 minutes. Normal score is regarded to be 7 and above. A total score of 3 or less is indicative of a critical condition, often combined with bluish color of the skin. This is named birth asphyxia due to insufficient respiration and circulation caused by problems in the umbilical cord or infection. In such case it is necessary within 5 minutes to establish free respiratory passages and restore normal circulation with fluid and/or medicaments. The umbilical vein is in the art regarded to be the most suitable port to inject adequate amounts of fluid into the central circulation of the neonates in order to reestablish normal circulation as quickly as possible.
Due to the anatomy and course of the umbilical vessels and that the cord of a neonate normally is slippery and compliant, the establishment of venous access through the umbilical vein is regarded technically difficult. When the neonate is critically ill, it is necessary to open up an infusion port within 5 minutes. It is often difficult to position a catheter 3-5 cm beyond the muco-cutaneous junction which is necessary to avoid is malpositioning of the catheter in the portal circulation and the accompanying possibility of hepatic necrosis. An established method is to insert the tips of an iris forceps into the vein and force the mouth of the vein open and insert the tip of the catheter.
Several methods to catheterize umbilical vessels are published in the art (US Patent Application Publication No 2009/062774, U.S. Pat. Nos. 8,105,308 and 4,585,437). U.S. Pat. No. 4,585,437 regards an improved device for introducing an umbilical artery catheter into an infant. The device consists of a funnel-like body with a handle-like member at the enlarged open end. At the end inserted into the arterial system, the small end of the funnel-like body consists of a plurality of prong-like nibs. The small end at the distal end of the prong-like nibs is bulbous-like and serves to prevent the device from being extruded from the arterial system once it is in place. U.S. Pat. No. 8,105,308 provides a method and an apparatus for catheterization of umbilical vessels in a newborn wherein the tube will remain permanently at the location. The method comprises inserting, with a guiding member, a tube into an umbilical vessel in an umbilical cord prior to occlusion of the umbilical vessel, wherein the tube is configured to have dimensions so that the tube remains in a fixed position within the umbilical vessel both prior to and after the occlusion of the umbilical vessel. The tube has a first end and a second end wherein the second end is closed and a valve operably connected to the first end of the tube and configured to provide access to the interior of the tube to the guiding member, wherein the tube is impermeable, removing the guiding member from the tube and clamping the umbilical cord, whereby the tube is permanently placed within the umbilical vessel of the newborn. US Patent Application Publication No 2009/062774 provides an invention relating to a device for introducing a silicone catheter by the umbilical route. The introducing device comprises polyurethane catheter in which the silicone catheter can slide, and a rectilinear and rigid tube which is made of stainless metal and is shorter than the catheter and whose internal diameter is adapted to the external diameter of the silicone catheter in order to allow the silicone catheter to slide in the metal tube, while preventing entry of air between them. This metal tube is introduced into the proximal end of the polyurethane catheter and fixed to said catheter in such a way as to prevent entry of air between them. This invention applies in particular to the catheterization of premature babies or neonates.
None of the above described methods and devices prove useful to apply when reviving critically ill neonates of mammalian origin, especially when the time factor is critical. Usually such catheterization is performed with long intervals by the skilled person in the art who therefore lacks training in the procedure. Thus there is a need in the art for is an improved method which can be performed by the skilled person without the need for repetitive training.
Thus the object of the present invention is to provide a device and method for introducing and maintaining a port in an umbilical vessel in mammalian neonates. The device is easily positioned by health personell normally attending the childbirth, such as doctors, midwifes and nurses. No specialized skills and particular experience are required.